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.Dd May 5, 2020
.Dt THR_KILL 2
.Os
.Sh NAME
.Nm thr_kill
.Nd send signal to thread
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/thr.h
.Ft int
.Fn thr_kill "long id" "int sig"
.Ft int
.Fn thr_kill2 "pid_t pid" "long id" "int sig"
.Sh DESCRIPTION
The
.Fn thr_kill
and
.Fn thr_kill2
system calls allow sending a signal, specified by the
.Fa sig
argument, to some threads in a process.
For the
.Fn thr_kill
function, signalled threads are always limited to the current process.
For the
.Fn thr_kill2
function, the
.Fa pid
argument specifies the process with threads to be signalled.
.Pp
The
.Fa id
argument specifies which threads get the signal.
If
.Fa id
is equal to \-1, all threads in the specified process are signalled.
Otherwise, only the thread with the thread identifier equal to the
argument is signalled.
.Pp
The
.Fa sig
argument defines the delivered signal.
It must be a valid signal number or zero.
In the latter case no signal is actually sent, and the call is used to
verify the liveness of the thread.
.Pp
The signal is delivered with
.Dv siginfo
.Dv si_code
set to
.Dv SI_LWP .
.Sh RETURN VALUES
If successful,
.Fn thr_kill
and
.Fn thr_kill2
will return zero, otherwise \-1 is returned, and
.Va errno
is set to indicate the error.
.Sh ERRORS
The
.Fn thr_kill
and
.Fn thr_kill2
operations return the following errors:
.Bl -tag -width Er
.It Bq Er EINVAL
The
.Fa sig
argument is not zero and does not specify valid signal.
.It Bq Er ESRCH
The specified process or thread was not found.
.El
.Pp
Additionally, the
.Fn thr_kill2
may return the following errors:
.Bl -tag -width Er
.It Bq Er EPERM
The current process does not have sufficient privilege to check existence or
send a signal to the specified process.
.El
.Sh SEE ALSO
.Xr _umtx_op 2 ,
.Xr kill 2 ,
.Xr thr_exit 2 ,
.Xr thr_new 2 ,
.Xr thr_self 2 ,
.Xr thr_set_name 2 ,
.Xr pthread_kill 3 ,
.Xr signal 3
.Sh STANDARDS
The
.Fn thr_kill
and
.Fn thr_kill2
system calls are non-standard and are used by the
.Lb libthr
to implement
.St -p1003.1-2001
.Xr pthread 3
functionality.
.Sh HISTORY
The
.Fn thr_kill
and
.Fn thr_kill2
system calls first appeared in
.Fx 5.2 .
